/*
 cdecoder.c - c source to a base64 decoding algorithm implementation

 This is part of the libb64 project, and has been placed in the public domain.
 For details, see http://sourceforge.net/projects/libb64
 */

#include "../../include/util/cdecode.h"

int base64_decode_value(char value_in)
{
	static const char decoding[] =
	{ 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1,
			-2, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
			15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1,
			26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42,
			43, 44, 45, 46, 47, 48, 49, 50, 51 };
	static const char decoding_size = sizeof(decoding);
	value_in -= 43;
	if (value_in < 0 || value_in > decoding_size)
		return -1;
	return decoding[(int) value_in];
}

void base64_init_decodestate(base64_decodestate* state_in)
{
	state_in->step = step_a;
	state_in->plainchar = 0;
}

int base64_decode_block(const char* code_in, const int length_in,
		char* plaintext_out, base64_decodestate* state_in)
{
	const char* codechar = code_in;
	char* plainchar = plaintext_out;
	char fragment;

	*plainchar = state_in->plainchar;

	switch (state_in->step)
	{
	while (1)
	{
		case step_a:
		do
		{
			if (codechar == code_in + length_in)
			{
				state_in->step = step_a;
				state_in->plainchar = *plainchar;
				return plainchar - plaintext_out;
			}
			fragment = (char) base64_decode_value(*codechar++);
		} while (fragment < 0);
		*plainchar = (fragment & 0x03f) << 2;
		case step_b:
		do
		{
			if (codechar == code_in + length_in)
			{
				state_in->step = step_b;
				state_in->plainchar = *plainchar;
				return plainchar - plaintext_out;
			}
			fragment = (char) base64_decode_value(*codechar++);
		} while (fragment < 0);
		*plainchar++ |= (fragment & 0x030) >> 4;
		*plainchar = (fragment & 0x00f) << 4;
		case step_c:
		do
		{
			if (codechar == code_in + length_in)
			{
				state_in->step = step_c;
				state_in->plainchar = *plainchar;
				return plainchar - plaintext_out;
			}
			fragment = (char) base64_decode_value(*codechar++);
		} while (fragment < 0);
		*plainchar++ |= (fragment & 0x03c) >> 2;
		*plainchar = (fragment & 0x003) << 6;
		case step_d:
		do
		{
			if (codechar == code_in + length_in)
			{
				state_in->step = step_d;
				state_in->plainchar = *plainchar;
				return plainchar - plaintext_out;
			}
			fragment = (char) base64_decode_value(*codechar++);
		} while (fragment < 0);
		*plainchar++ |= (fragment & 0x03f);
	}
	}
	/* control should not reach here */
	return plainchar - plaintext_out;
}
